Peroxisome proliferator-activated receptor (PPAR) is a member of the nuclear receptor superfamily of ligand activated transcription factor. Three subtypes of PPAR, i.e., PPAR α, PPAR γ, and PPAR δ, have been cloned from mouse and human. PPAR is known as an important nuclear hormone receptor for the metabolism of carbohydrate and lipid, immunoregulation, and inflammatory reaction. It has been reported that compounds that activate PPAR are useful for the treatment and prophylaxis of various clinical diseases such as metabolic syndrome, obesity, prediabetes, type 2 diabetes and the other insulin resistance syndrome, hypertension, atherosclerosis, lipemia, inflammatory skin diseases such as psoriasis, inflammatory bowel disease, and inflammatory neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease etc., and the like. PPAR γ specifically is said to play an important role in adipocyte differentiation. Hypertrophic adipocytes secrete large amounts of cytokines, namely TNF-α and free fatty acid which induce insulin resistance. On the other hand, it has been reported that thiazolidinedione derivatives such as pioglitazone, rosiglitazone and the like improve insulin resistance by activating PPAR γ to decrease hypertrophic adipocytes by apoptosis, and promoting differentiation of preadipocytes into small adipocytes having normal function (non-patent documents 1 and 2). Pioglitazone and rosiglitazone, which are PPAR γ agonists, have already been clinically used as therapeutic drugs for diabetes (patent documents 1 and 2).
PPAR γ agonists are also useful as agents for treating and/or preventing diseases besides diabetes, such as metabolic syndrome, obesity, impaired glucose tolerance and other insulin resistance syndrome, which are prediabetic conditions, hypertension, atherosclerosis, hyperlipidemia, inflammatory diseases such as psoriasis and the like, inflammatory bowel disease, and the like.
It has been reported that selective partial agonists for PPAR γ do not accompany side effects such as body weight increase, adipocyte accumulation and the like, as compared to the existing full agonists (thiazolidinedione derivative or the like) (non-patent document 3).
A tricyclic compound represented by the following formula (A) and a derivative thereof are known as PPAR agonists/antagonists/regulators (patent document 3).

It is known that a compound represented by the following formula (B), which is a tricyclic compound, and a derivative thereof have a superior hypotensive action based on an angiotensin II receptor antagonistic action (see patent document 4).

A compound represented by the following formula (C), which is a tricyclic compound, and a derivative thereof are known as PPARγ agonists (see patent document 5).
